1. Field of Invention
The invention relates to antenna for hand-held telecommunication devices and more particularly to a broadband multi-loop antenna mounted in a mobile communication device (e.g., cellular phone).
2. Description of Related Art
The development trend of antenna for a hand-held telecommunication device (e.g., cellular phone) is an antenna capable of operating in multi-band (e.g., GSM 800/900/1800/1900 Hz, and/or WLAN 2.4 GHz/5.1 GHz/5.8 GHz), being high in gain, and working well in one of a plurality of states of the cellular phone (e.g., folding, open, hand-held, waist hanging, or resting upon a desk). Moreover, antennas for cellular phone are typically mounted therein (i.e., internal antennas) for purposes including aesthetics, durability, portability, etc. Such internal antenna is typically capable of operating in dual-band (i.e., GSM 900 Hz and GSM 1800 Hz; GSM 850 Hz and GSM 1900 Hz); or tri-band (i.e., GSM 900 Hz, GSM 1800 Hz and GSM 1900 Hz; or GSM 850 Hz, GSM 1800 Hz and GSM 1900 Hz). It is desired by the cellular phone manufacturers to produce a cellular phone having an antenna capable of operating in four different bands so as to reduce the manufacturing cost, be more competitive in the market, and have other beneficial advantages.
United States Patent Application Number 2004/0075610 discloses a PIFA antenna apparatus for mobile communications terminals as shown in FIG. 1A. The PIFA antenna comprises an HF input/output and two antenna surfaces respectively having a connecting point to the ground plane of a mobile communication terminal. The first antenna surface is configured for two independent frequencies and the second antenna surface 1000 is configured for a third independent frequency. Only the first antenna surface is connected to the HF input/output and the second antenna surface is arranged in a non-contact manner with respect to the first antenna surface, whereby an electromagnetic coupling occurs between both antenna surfaces.
United States Patent Application Number 2003/0052824 discloses an internal multi-band antenna with improved radiation efficiency as shown in FIG. 1B in which a third radiating element 1000 is provided for effecting multi-band operation.
Another conventional proposal for effecting a multi-band antenna is characterized by increasing the number of loops as shown in FIG. 1C. However, grounding points 1 and 2 are common for a plurality of loops. Thus, it is low in performance.
All of the above prior art failed to effect an antenna capable of operating in quad-band. Thus, the need for innovative improvement still exists.